LOS ANGELES - UPDATE: In updated "fast national" results from Nielsen for Sunday night, ABC's telecast of the Academy Awards averaged 36.6 million viewers and a 10.8 rating in adults 18-49 -- declines of 16% and 18% respectively from last year (43.7 million and 13.1). The total-viewer count is the event's lowest in six years.

This year's Oscars ceremony has joined other award shows from this television season in posting year-over-year ratings declines, down 10% in the overnights from last year's decade-best score.

According to Nielsen overnight estimates measuring 56 of the nation's biggest markets, last night's "87th Annual Academy Awards" telecast on ABC, hosted by first-timer Neil Patrick Harris, averaged a 25.0 household rating/38 share, the show's lowest rating since a 24.5 in 2011. Nielsen will issue total-viewer estimates for last night's show later today.

Los Angeles ranked as the top-rated market for the Oscars (33.5 household rating), up 3% from last year. But key to the ratings declines overall were double-digit falloffs in both New York (down 13% to 32.4) and Chicago (down 10% to 32.5).

Last year's show, hosted by Ellen DeGeneres, averaged a 27.9 overnight household rating/41 share that translated into a 10-year best 43.74 million viewers, according to Nielsen -- the third time in five years the Oscars had been above the 40-million viewer mark. And in adults 18-49, its 13.1 rating/33 share in the nationals was up a smidge from 2013 for a four-year high.

With social media driving interest, awards shows in general had been on a ratings roll. But some of the air seems to have come out of the balloon this season.

Earlier this month, the Grammy Awards on CBS (8.3 rating/23 share in adults 18-49, 24.82 million viewers overall) were down 16% in the demo and 13% in total viewers from last year for the show's lowest numbers in six years. Still, the kudocast figures to finish the season ranked second to the Oscars among the top-rated non-football programs.

Last night's Oscars did a 14.2 rating in adults 18-49, according to Nielsen's LPM (Local People Meter) markets, down just slightly from last year (14.4) and solidly above the 9.9 earned by the Grammys on Feb. 8.

Adults 18-49 ratings were also lower this season for the "CMA Awards" on ABC (down 4%, 4.5 vs. 4.7), the "American Music Awards" on ABC (down 16%, 3.8 vs. 4.5) and the "Golden Globe Awards" on NBC (down 11%, 5.8 vs. 6.5).

In social media, 21 million people had 58 million interactions (posts, comments, likes) related to the Oscars on Facebook on Sunday. The top moment was Lady Gaga's medley from "The Sound of Music" and Julie Andrews joining her on stage, which drew 214,000 per minute globally and 145,000 per minute in the States; this was also the top moment on Twitter for the night.

ABC towered over its rivals last night, with its 7 to 11 p.m. household average in the metered-market overnights more than tripling its combined CBS-NBC-Fox competition (20.4 vs. 6.6). And in adults 18-49, it drew six times those net's combined averages (11.4 vs. 1.9).

A dearth of diversity among nominees and unfamiliarity with some of the most honored films may have contributed to the lower tune-in for the 2015 Oscars. Of this year's best picture nominees -- "American Sniper," "Birdman," "Boyhood," "The Grand Budapest Hotel," "The Imitation Game," "Selma," "The Theory of Everything," and "Whiplash" -- only "Sniper" can be considered a box office hit in North America.

"Birdman" was the big winner of the night, winning the top prize as well as others including best original screenplay and best director for Alejandro Gonzalez Inarritu.